Billionaire investor Carl Icahn has cut his stake in offshore driller Transocean Ltd. by 75 percent for tax reasons, following a similar sale of Chesapeake Energy Corp. shares last week.

Transocean was up 6.6 percent at $10.68 at 2:39 p.m. in New York as oil rallied for a second day following news that OPEC members agreed on the framework of a deal to reduce output. Icahn holds 5.48 million shares, or about a 1.5 percent stake, down from 21.5 million shares on June 30, according to a filing Wednesday.

Shares of the world’s biggest offshore drilling rig operator have been battered this year along with other deepwater drillers, sinking 24 percent through Tuesday as demand for its services dried up amid the worst oil slump in a generation. The company has resorted to shutting down and storing some of its $500 million rigs off Trinidad and Tobago in the Caribbean Sea in an effort to reduce costs.

Icahn said he believes the Vernier, Switzerland-based company’s executive team has "done an outstanding job given the challenging environment," according to a statement in the filing. He added that he continues to have confidence in the management.

Last week the billionaire reported he’d cut his stake in Chesapeake, also citing "tax planning purposes" and emphasizing that he retained confidence in the Oklahoma City-based gas company.